Transition Energies Research Articles

Enhancing the Photovoltaic Efficiency of In0.2Ga0.8N/GaN Quantum Well Intermediate Band Solar Cells Using Combined Electric and Magnetic Fields

This study presents a theoretical investigation into the photovoltaic efficiency of InGaN/GaN quantum well-based intermediate band solar cells (IBSCs) under the simultaneous influence of electric and magnetic fields. The finite element method is employed to numerically solve the one-dimensional Schrödinger equation within the framework of the effective-mass approximation. Our findings reveal that electric and magnetic fields significantly influence the energy levels of electrons and holes, optical transition energies, open-circuit voltages, short-circuit currents, and overall photovoltaic conversion performances of IBSCs. Furthermore, this research indicates that applying a magnetic field positively influences conversion efficiency. Through the optimization of IBSC parameters, an efficiency of approximately 50% is achievable, surpassing the conventional Shockley–Queisser limit. This theoretical study demonstrates the potential for next-generation photovoltaic technology advancements.

Room‐temperature magnetocapacitance spanning 97 K hysteresis in molecular material

Magnetic capacitor, as a new type of device, has broad application prospects in fields such as magnetic field sensing, magnetic storage, magnetic field control, power electronics and so on. Traditional magnetic capacitors are mostly assembled by magnetic and capacitive materials. Magnetic capacitor made of a single material with intrinsic properties is very rare. This intrinsic property is magnetocapacitance (MC). The studies on MC effect have mainly focused on metal oxides so far. No study was reported in molecular materials. Herein, two complexes: (CETAB)2[CuCl4] (1) and (CETAB)2[CuBr4] (2) (CETAB = (2‐chloroethyl)trimethylammonium) are reported. There exist strong H‐Br and Br‐Br interactions and other weak interactions in complex 2, so the phase transition energy barrier is high, resulting in the widest thermal hysteresis loop on a molecular level to date. Furthermore, complexes 1 and 2 show large MC parameters of 0.247 and 1.614, respectively, which is the first time to observe MC effect in molecular material.

Room-temperature magnetocapacitance spanning 97 K hysteresis in molecular material.

Magnetic capacitor, as a new type of device, has broad application prospects in fields such as magnetic field sensing, magnetic storage, magnetic field control, power electronics and so on. Traditional magnetic capacitors are mostly assembled by magnetic and capacitive materials. Magnetic capacitor made of a single material with intrinsic properties is very rare. This intrinsic property is magnetocapacitance (MC). The studies on MC effect have mainly focused on metal oxides so far. No study was reported in molecular materials. Herein, two complexes: (CETAB)2[CuCl4] (1) and (CETAB)2[CuBr4] (2) (CETAB = (2-chloroethyl)trimethylammonium) are reported. There exist strong H-Br and Br-Br interactions and other weak interactions in complex 2, so the phase transition energy barrier is high, resulting in the widest thermal hysteresis loop on a molecular level to date. Furthermore, complexes 1 and 2 show large MC parameters of 0.247 and 1.614, respectively, which is the first time to observe MC effect in molecular material.

Thermal Quenching Mechanism of Mn4+ in Na2SiF6, NaKSiF6, and K2SiF6 Phosphors: Insights from the First-Principles Analysis.

This study aims to identify the key factors governing the thermal quenching of Mn4+ ion luminescence in fluoride-based phosphor materials used as red emitters in modern-day phosphor-converted LED devices. Here, we employ first-principles calculations for Mn4+-doped Na2SiF6, NaKSiF6, and K2SiF6 hosts to explore how host properties and local coordination environments influence thermal quenching behavior. The ΔSCF method was used to model the geometric structures of the Mn4+4A2 (ground) and 2E, 4T2 (excited) states and the energies of the optical transitions between these states. Our results reveal that thermal quenching in Na2SiF6 and K2SiF6 phosphors occurs through thermally activated 2E → 4T2 → 4A2 crossover. In contrast, thermal quenching in NaKSiF6 is due to other nonradiative decay pathways. Investigations of the mechanical stability of these fluorides show that NaKSiF6 is mechanically unstable. We suggest that this property of the host limits the luminescence efficiency of the embedded Mn4+ ions. We also determined the reason for the difference in the intensity of the 2E → 4A2 emission transition (ZPL) in the systems. These findings advance our fundamental understanding of the thermal quenching mechanism of Mn4+ ion luminescence in fluorides, and the results can aid future discoveries of technologically useful phosphors through high-throughput design methodologies.

Near-Infrared Room-Temperature Phosphorescence from Monocyclic Luminophores.

Compact luminophores with long emission wavelengths have aroused considerable theoretical and practical interest. Organics with room-temperature phosphorescence (RTP) are also desirable for their longer lifetimes and larger Stokes shifts than fluorescence. Utilizing the low electronic transition energy intrinsic to thiocarbonyl compounds, electron-withdrawing groups were attached to the 4H-pyran-4-thione core to further lower the excited state energies. The resulting mini-phosphors were doped into suitable polymer matrices. These purely organic, amorphous materials emitted near-infrared (NIR) RTP. Having a molar mass of only 162 g·mol-1, one of the phosphors emitted RTP that peaked at 750 nm, with a very large Stokes shift of 15485 cm-1 (403 nm). Thanks to the good processability of the polymer film, light-emitting diodes (LEDs) with NIR emission were easily fabricated by coating doped polymer on ultraviolet LEDs. This work provides an intriguing strategy to achieve NIR RTP using compact luminophores.

Near‐Infrared Room‐Temperature Phosphorescence from Monocyclic Luminophores

Compact luminophores with long emission wavelengths have aroused considerable theoretical and practical interest. Organics with room‐temperature phosphorescence (RTP) are also desirable for their longer lifetimes and larger Stokes shifts than fluorescence. Utilizing the low electronic transition energy intrinsic to thiocarbonyl compounds, electron‐withdrawing groups were attached to the 4H‐pyran‐4‐thione core to further lower the excited state energies. The resulting mini‐phosphors were doped into suitable polymer matrices. These purely organic, amorphous materials emitted near‐infrared (NIR) RTP. Having a molar mass of only 162 g·mol‐1, one of the phosphors emitted RTP that peaked at 750 nm, with a very large Stokes shift of 15485 cm‐1 (403 nm). Thanks to the good processability of the polymer film, light‐emitting diodes (LEDs) with NIR emission were easily fabricated by coating doped polymer on ultraviolet LEDs. This work provides an intriguing strategy to achieve NIR RTP using compact luminophores.

Urban-scale power decarbonization using a modified power purchase agreements framework based on Markowitz mean-variance theory

Urban power decarbonization is essential in the fight against climate change, yet current research often neglects the financial risks faced by investors and the shifting demands of consumers in liberalized electricity markets. This study addresses these gaps by proposing a modified Markowitz Mean-Variance Portfolio (MVP) theory, integrated with the Low Emissions Analysis Platform (LEAP), and a deep learning model. On this basis, an urban energy transition framework centered on Power Purchase Agreements (PPAs) is proposed and developed. The framework is validated considering a case study in Kitakyushu, Japan, highlighting its potential in accelerating power sector decarbonization and achieving net-zero emissions by 2038. Additionally, the internal rate of return (IRR) remains stable between 14.5 % and 19.6 % across seven other cities. While the framework reduces long-term cash flow volatility, its effectiveness hinges on industrial electrification efficiency and regional energy self-sufficiency. The findings indicate that relying solely on renewable energy for low-carbon transitions is unrealistic. Furthermore, green hydrogen could emerge as a viable alternative to fossil fuels, potentially replacing batteries for long-term energy storage. Future research should explore cross-regional energy trade and establish legal frameworks for long-term energy transactions to bolster urban energy transition resilience across diverse geographic and economic contexts.

DFT study of electronic and nonlinear optical properties of alkaline earth metals and superalkalis doped all-cis-1, 2, 3, 4, 5, 6-hexafluorocyclohexane as an efficient excess electron system

Continual advancements are being pursued to discover innovative strategies for developing materials with remarkable nonlinear optical (NLO) response. Herein, electronic, geometric, thermodynamic and NLO properties of excess electron systems based on stacked Janus dimer, all-cis-1,2,3,4,5,6-hexafluorocyclohexane (C6H6F6)2 are thoroughly investigated. The excess electron systems are designed by doping alkaline earth metals (AEMs) on fluorine face and superalkalis on hydrogen face of Janus dimer. The higher values of vertical ionization energies (VIE) and interaction energies (Eint), confirm the electronic and thermodynamic stabilities of the designed complexes, respectively. Natural bond orbital (NBO) analysis is performed, and the excess electron character of the complexes is confirmed through frontier molecular orbital (FMO) analysis by highest occupied molecular orbital (HOMO) iso-densities. FMO shows a significant decrease in energy gaps (Egap) of the complexes (i.e., Eg = 1.80–3.12 eV), compared to the stacked Janus dimer (i.e., Eg = 9.41 eV). The transparency of the complexes to UV region is confirmed through UV–vis analyses, revealing their maximum absorption in visible and near-IR regions. The higher NLO response of the designed excess electron systems is further proved by the greater values of first hyperpolarizability (β o ) i.e., up to 1.70 × 106 au. Moreover, the time dependent-density functional theory (TD-DFT) computations and two-level model are employed to investigate the controlling factors of hyperpolarizability, illustrating the contribution of transition energy (∆E3), change in dipole moment (∆μ) and oscillator strength (f o ) in controlling the β o . Ab-initio molecular dynamics (AIMD) simulation further confirm that the designed superalkalide complexes are kinetically and thermally stable. The thorough investigation of these excess electron systems proves them an appropriate candidate for NLO applications.

Estimating a national critical mineral security index in Indonesia using analytical hierarchy process

Critical minerals are key to guaranteeing energy security and economic stability in a nation. Indonesia, as the largest country in Southeast Asia, has significant reserves of critical minerals. The current circumstances, however, pose substantial challenges for Indonesia as it strives for self-sufficiency in various sectors. Indonesia must pay attention to its natural resource management, especially that of critical minerals. This study aims to present information on securing critical mineral resources in Indonesia by constructing a Critical Mineral Security Index (CMSI). This study used a quasi-qualitative method, wherein the Analytical Hierarchy Process (AHP) was used as the process of analysis. A total of four dimensions have been proposed in this study—availability, accessibility, technology-efficiency, and environmental, social, and governance (ESG) dimensions with a total of 29 indicators. The results of the AHP confirm that the security level of critical mineral resources in Indonesia is 5.57. The results indicate that the availability dimension has the highest weight compared to the other dimensions, equal to 47.6%. While the accessibility dimension has the lowest level of resistance. The government should, therefore, prioritize improving the indicators of accessibility dimensions. These results have policy implications for the energy and mineral sector in the future, to further reinforce energy and mineral security on a national scale, which may ultimately support transition energy in Indonesia and strengthen national defense.

Thermoluminescence characteristics of UV-irradiated natural hackmanite

Hackmanite has received extensive attention from scholars in recent years. However, there is still no report on the thermoluminescence properties of natural hackmanites under UV irradiation, as well as its relative electron trap and luminescence center. In this paper, the structural defects and thermoluminescence spectroscopic properties of hackmanite are comprehensively characterized by XRD, TL spectroscopy, SEM, EPR, XPS and Raman spectroscopy. The traps depth of TL peaks are calculated by computerized glow curve deconvolution (CGCD) techniques. And the charge transition energy levels of intrinsic defects in Na8Al6Si6O24(Cl,S)2 are calculated by spin-polarized density-functional theory (DFT) in VASP. It shows that the low-temperature TL peaks of hackmanite are associated with Cl vacancies and photochromic properties. The high-temperature peak is caused by marginal oxygen vacancies. The results are conducive to deepening the understanding of structural defects of the hackmanites and linking the thermoluminescence with the phototropy.

Laser Spectroscopic Characterization of Supersonic Jet-Cooled 2,6-Diazaindole (26DAI).

The article presents a comprehensive laser spectroscopic characterization of a nitrogen-rich indole derivative, namely, 2,6-diazaindole (26DAI), in the gas phase. A supersonic jet-cooled molecular beam of 26DAI was characterized using two-color resonant two-photon ionization (2C-R2PI) and laser-induced fluorescence spectroscopy (LIF) to investigate the electronic excitation. The S1 ← S0 origin transition was obtained at 33915 cm-1, which was red-shifted from that of one (indole) and two (7-azaindole) nitrogen-containing indole derivatives by 1317 and 713 cm-1, respectively. The molecular orbital and energy analysis for the S1 ← S0 transition shows the significant stabilization of LUMO on subsequent N-insertion, resulting in the lowering of the S1 ← S0 (ππ*) transition energy. The single vibronic level fluorescence spectrum from the vibrationless S1 state of the molecule was recorded. The spectrum displayed an extensive Franck-Condon activity until 2500 cm-1 for the vibrational modes of the S0 state of the 26DAI molecule. The experimental ground state vibrational frequencies were compared to the calculated ones obtained at three different levels of theories. More accurate results were found at DFT B3LYP-D4 than those at the wave function-based MP2 and CCSD levels of theories. Further, the N-H stretching frequency of 26DAI in the S0 state was measured at 3524 cm-1 using fluorescence-dip infrared (FDIR) spectroscopy. The stability of 26DAI against ionization radiation was probed by measuring the two-color photoionization energy (IE2P) of 26DAI at 71866 cm-1. The IE2P value is significantly higher than those of N-poor counterparts (indole and 7-azaindole). The NBO charges and spin density (SD) values of the 26DAI molecule have shown that electronegative N(6) makes the cationic ground state less stable due to the position of the positive centers on the N atom. The results provided insights into the stability of N-rich biomolecules against photodamage. The current investigation can shed light on nature's way of stabilizing biomolecules with a possible N-insertion mechanism.

Ortho-Para Conversion for H+ + H2 Collision in Low Temperature: A Fully Close-Coupled Time-Dependent Wave Packet Study.

The collision-induced rate coefficients of ortho-para conversion for the H+ + H2 reaction provide accurate information to probe the lifetime of cold environments in interstellar media. Rotationally resolved reaction probabilities are calculated at the low collision energy regime (0 < Ecol ≤ 0.3 eV) by employing the coupled three-dimensional (3D) time-dependent wave packet (TDWP) formalism in hyperspherical coordinates on a recently constructed ab initio ground adiabatic potential energy surface of H3+ [J. Chem. Phys. 2014, 141, 204306] for the process H+ + H2 (v = 0, j = 0-5) → H+ + H2 (v' = 0, j'). Cross-sections are then computed from the converged reaction probabilities as a function of total angular momentum (J) over the same energy regime and subsequently employed to obtain the rate constants for the ortho-to-para (O-P) and para-to-ortho (P-O) conversions and their ratio. The ratio of ortho-para conversion shows (a) appropriate convergence with the inclusion of a higher number of initial rotational states as well as a reasonable agreement with the results from a quantum statistical method and (b) a peak at lower temperature that could be due to the available collision energy for transitions involving lower rotational states (j = 0 → j' = 1).

Isolation of Single Donors in ZnO.

The shallow donor in zinc oxide (ZnO) is a promising semiconductor spin qubit with optical access. Single indium donors are isolated in a commercial ZnO substrate using plasma focused ion beam (PFIB) milling. Quantum emitters are identified optically by spatial and frequency filtering. The indium donor assignment is based on the optical bound exciton transition energy and magnetic dependence. The emission stability of these single donors in terms of both intensity and frequency, alongside their transition linewidths less than twice the lifetime limit, highlight the promise of single In donors as optically accessible spin qubits. The optical stability of single donors after FIB fabrication is promising for optical device integration required for scalable quantum technologies based on single donors in direct band gap semiconductors.

Spectroscopic and Computational Study of Vanillin-Dipyrrin Ligand that Capable of Colorimetric Sensor for Zinc and Copper Ions

Phenolic-dipyrrin is a promising colorimetric chemosensor due to its tautomeric formation (phenolic-hemiquinone forms). In methanol solution, the vanillin-dipyrrin compound exists as a hemiquinone species, whereas the complexes exist in a phenolic form. This molecule showed a red-magenta color in methanol, in contrast to yellowish allyl-protected-dipyrrin. In the presence of zinc or copper ions, the vanillin-dipyrrin solution turned into a pale-yellow complex, similar to that of protected-dipyrrin. A computational study of the ligands and complexes showed a close relevance, where the energy transition between the highest molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the ligand in the hemiquinone form had a lower energy transition, and the two complexes showed slightly different transition energies. Apart from naked-eye color changes, vanillin-dipyrrin showed limits of detection of 9.2 × 10–7 M and 4.8×10−7 M for zinc and copper ions, respectively.

Neutral donors confined in semiconductor coupled quantum dot-rings: Position-dependent properties and optical transparency phenomenon

Electronic properties of a neutral donor confined in a GaAs coupled quantum dot-ring covered by a Al0.3Ga0.7As matrix were calculated using the finite element method under the effective mass and the envelope function approximations. The proposed model is set up to fit a realistic coupled quantum dot-ring geometry revealed by atomic force microscopy images. The results show that the energy levels and the transition energies in the presence of an electric field strongly depend on the donor center’s angular position. Furthermore, the total optical absorption coefficient is calculated within the two-level approximation and the matrix density formalism. The absorption spectrum shows that the system can be tuned between 5 and 30meV. Also, an optical transparency effect for different configurations characterized by specific donor center’s angular positions and electric field values is seen. Finally, a novel redshift is observed when the sample temperature increases.

Dynamic role of climate change, energy innovation and renewable energy on energy transition in USA: Fresh insights from green finance development

Over the past, all the big economies across the world are focusing on attainment of objectives of COP27 and COP28 and USA is forefront among them. Therefore, present study aims to unraveling the role of renewable energy, energy innovation, climate change and green financial development in mapping and shaping the energy transition system in the USA. In view of this, study utilizes annual data of said constructs from 2008 to 2022 and estimates through Dynamic Autoregressive Distributed Lag simulations (DARDLS) approach. Results indicate the positve impacts of renewable energy and energy innovation on energy transition and sustainable energy management in both long and short run. Whereas green financial development reflects low positive impact on energy transition in short run and getting stronger in long run. Expectedly, climate change adversely affect the energy transition and increases energy risk for the USA. Policy implications and Government frameworks are suggested to facilitate the renewable energy, energy innovation and green financial development and to mitigate climate change risk in USA.

Influence of terminal moiety on PCE of DSSCs: An In Silico study based on triazatruxene-benzothiadiazole dye

Our study utilized an experimentally synthesized dye as a reference molecule, employing a donor-π linker-acceptor (D-π-A) framework for organic solar cells. The molecule featured a triazatruxene group linked with alkyl branches as the donor and ethynyl benzoic acid as the acceptor, connected through a derivative of benzothiadiazole as the π linker. To improve optoelectronic and photovoltaic properties, ten theoretically designed dyes (ZA1–ZA10) are proposed, differing from the reference (R) by modifying the terminal acceptor moiety. Various quantum analyses, including frontier molecular orbitals, optical properties, reorganization energies, binding energies, transition density matrices (TDM), molecular electrostatic potential (MEP), dipole moment, and density of states were carried out at DFT/B3LYP/6-31G(d,p). Ground state geometries revealed a co-planar morphology in ZA1–ZA10, facilitating efficient charge transportation. TDM and MEP illustrated improved electronic transitions in the excited states. Computational analyses revealed superior photovoltaic properties of ZA1–ZA10. Notably, ZA5 exhibited the most significant redshift (1021 nm) in absorption, lowest bandgap (1.44 eV), smallest transition energy (1.21 eV), least binding energy (0.23 eV), and improved charge mobilities. Results from the adsorption of ZA1-ZA10 on the TiO2 layer confirmed their anchoring potential and effective injection of electrons to anatase (TiO2)9. These significant outcomes promise the potential and novelty of our designed dyes for higher power conversion efficiencies (PCE) in dye-sensitized solar cells (DSSCs).

Simultaneous Proton and Electron Energization during Macroscale Magnetic Reconnection

The results of simulations of magnetic reconnection accompanied by electron and proton heating and energization in a macroscale system are presented. Both species form extended power-law distributions that extend nearly three decades in energy. The primary drive mechanism for the production of these nonthermal particles is Fermi reflection within evolving and coalescing magnetic flux ropes. While the power-law indices of the two species are comparable, the protons overall gain more energy than electrons, and their power law extends to higher energy. The power laws roll into a hot thermal distribution at low energy with the transition energy occurring at lower energy for electrons compared with protons. A strong guide field diminishes the production of nonthermal particles by reducing the Fermi drive mechanism. In solar flares, proton power laws should extend down to tens of keV, far below the energies that can be directly probed via gamma-ray emission. Thus, protons should carry much more of the released magnetic energy than expected from direct observations.

Fabrication of Textured 0.685(Na0.5Bi0.5)TiO3-0.065BaTiO3-0.25SrTiO3 Electrostrictive Ceramics by Templated Grain Growth Using NaNbO3 Templates and Characterization of Their Electrical Properties

Electrostrictive materials based on (Na0.5Bi0.5)TiO3 are promising lead-free candidates for high-precision actuation applications, yet their properties require further improvement. This study aims to enhance the electromechanical properties of a predominantly electrostrictive composition, 0.685(Na0.5Bi0.5)TiO3-0.065BaTiO3-0.25SrTiO3, by using templated grain growth. Textured ceramics were prepared with 1~9 wt% NaNbO3 templates. A high Lotgering factor of 95% was achieved with 3 wt% templates and sintering at 1200 °C for 12 h. Polarization and strain hysteresis loops confirmed the ergodic nature of the system at room temperature, with unipolar strain significantly improving from 0.09% for untextured ceramics to 0.23% post-texturing. A maximum normalized strain, Smax/Emax (d33*), of 581 pm/V was achieved at an electric field of 4 kV/mm for textured ceramics. Textured ceramics also showed enhanced performance over untextured ceramics at lower electric fields. The electrostrictive coefficient Q33 increased from 0.017 m4C−2 for untextured ceramics to 0.043 m4C−2 for textured ceramics, accompanied by reduced strain hysteresis, making the textured 0.685(Na0.5Bi0.5)TiO3-0.065BaTiO3-0.25SrTiO3 composition suitable for high-precision actuation applications. Dielectric properties measured between −193 °C and 550 °C distinguished the depolarization, Curie–Weiss and Burns temperatures, and activation energies for polar nanoregion transitions and dc conduction. Dispersive dielectric constants were found to observe the “two” law exhibiting a temperature dependence double the value of the Curie–Weiss constant, with shifts of about 10 °C per frequency decade where the non-dispersive THz limit was identified.

Optical Properties of Multilayered Staggered SiGe Nanodots Depending on Si Spacer Growth Temperature

The optical properties of the multilayered staggered SiGe nanodots (NDs) embedded in the Si spacers fabricated at varying Si growth temperatures are clarified in conjunction with the effect of strain by Photoluminescence (PL) and Raman spectroscopy. We found that compressive strain is induced in the SiGe NDs, with higher growth temperatures of the Si spacer resulting in stronger compressive strain. PL spectra indicate that the higher growth temperature leads to a wider bandgap. This transition energy behavior is caused by not only the strain in the SiGe NDs but also the Ge segregation. Furthermore, luminescence from the SiGe NDs was observed along with luminescence originated at the Si/SiGe interface in the SiGe NDs with a small dot size. This phenomenon was caused by the small energy difference of the conduction-band minima between the SiGe NDs and the tensile-strained Si spacers and the small volume of the tensile-strained Si spacers.